How do Helicopters fly?

Helicopters were designed and attempted long before
planes came into existence. However, none of the attempts were
succesful long after plane's first flight. They are lot more complex
and many forces work on them.

Fundamental parts of any Helicopter:

Alike planes, Helicopters also have same 4 forces
working on them:

Thrust: Force that pushes the aircraft forward

Weight: Force that pulls the plane downward

Drag: Its kind of friction that tries to stop
plane from moving forward

Lift: Upward force that keeps the plane in
air

Helicopter gets Lift and Thrust from main
rotor. As they spin they cut into the air and produce
lift. Each blade produces an equal share of the lifting force.
Spinning the rotor against the air causes lift, allowing the helicopter
to rise vertically or hover. Tilting the spinning rotor will cause
flight in the direction of the tilt. This is the necessary forward
thrust. A very small amount of thrust that comes from engine exhaust,
but it is so small that it does not effect flight performance.

Importance of tail rotor: Due to
rotor's movement, it produces an opposing torque on helicopter,
thus causing it to move in the opposing direction. Tail rotor
helps counter the torque reaction by pulling against it.

Increasing the pitch angle of the tail rotor will
increase the thrust, which in turn will push the helicopter in
the same direction as the main rotor blades. Decreasing the pitch
angle decreases the amount of thrust, and so the natural torque
force takes over letting the helicopter rotate in the opposite
direction to the main rotors.

The pilot controls the pitch angle of the tail rotor
blades by two pedals at his feet, in exactly the same way as the
rudder movement is controlled in an airplane.